The present invention relates to a toner for the development of an electrostatic image for use in the development of an electrostatic latent image in electrophotography or electrostatic recording method, a process for the preparation thereof, a developer for the development of an electrostatic image, and a process for the formation of an image.
A method for rendering an image data visible via electrostatic image such as electrophotography has been used in various fields. In electrophotography, an electrostatic latent image is formed on a photoreceptor at a charging/exposure step. The electrostatic latent image is developed with a developer containing a toner, and then processed at a transferring step and a fixing step to become visible. Examples of the developer to be used in electrophotography include two-component developer comprising a toner and a carrier and one-component developer comprising a magnetic or non-magnetic toner alone. Such a toner is normally prepared by a knead-grinding method which comprises melt-kneading a thermoplastic resin with a pigment, a static controller and a release agent such as wax, cooling the mixture, finely grinding the mixture, and then classifying the particles. In this method, inorganic or organic particles may be attached to the surface of the toner particles to improve the fluidity or removability of the toner.
On the other hand, with the recent development of advanced information-oriented society, there has been a growing demand for the provision of data documents built by various methods in an even higher image quality. Thus, the enhancement of image quality is understudy in various arts of image formation. This demand has been given to every art of image formation, not excepting image formation methods using electrophotography. In electrophotography, the development of technique for reducing a particulate toner having a reduced particle diameter and a sharp grain size distribution and making toner particles spherical is now under way to realize an even higher precision in color image formation.
Referring to the process for making toner particles spherical, the shape of the resulting toner particles has an effect on the precision in transferring of toner particles at the transferring step. The more spherical the toner particles can be kept until the final image is obtained, the smaller is the contact area of the toner particles with the carrier and hence the higher is the precision in transferring of toner particles and the more can be expected the enhancement of final image quality such as reproducibility of fine line.
However, there is a problem that when such spherical toner particles are used, the toner particles which have been left untransferred from the carrier can be hardly removed.
In order to remove the untransferred toner, a method using a blade is widely used because the device is simple and durable. In this blade cleaning method, however, it is much likely that spherical toner particles can be passed by the blade because of its shape, causing poor removability leading to deterioration of image quality. Thus, the art must consider how spherical toner particles used for higher image quality can be removed.
In order to solve this problem, some approaches have been attempted. One of these approaches is to raise the linear pressure applied to the edge of the blade, preventing the toner particles from being passed by the blade. However, this approach is disadvantageous in that the mere rise in linear pressure accelerates the abrasion of the edge of the blade and the carrier and causes the blade to vibrate and give noise.
In order to eliminate such noise and abrasion, an approach has been proposed which comprises supplying a particulate lubricant into the edge of the blade to reduce the friction coefficient of the edge of the blade. In order to efficiently reduce the friction coefficient of the edge of the blade with a lubricant thus supplied, the particle diameter of the particulate lubricant is preferably as small as about 0.2 xcexcm or less. However, these submicron lubricant particles can be scattered inside the machine, staining the static charger or like parts and hence causing malcharging or like defects. The resulting image has a deteriorated quality.
Further, an approach has been proposed which comprises supplying onto the edge of the blade submicron irregular shape inorganic particles that then form a sealing material on the edge of the blade to make it difficult for spherical toner particles to be passed by the blade. This approach is based on a mechanism that spherical toner particles which can be otherwise easily passed by the blade are trapped by irregular shape particles such as irregular shape silica and alumina which have been supplied onto the blade of the blade. However, this approach, too, is disadvantageous in that the particle diameter of the irregular shape particles needs to be about 0.2 xcexcm or less to be efficiently supplied onto the edge of the blade and prevent the spherical toner particles from being passed by the blade similarly to the foregoing lubricant. In this approach, too, problems arise as in the case of the foregoing lubricant.
Therefore, an object of the present invention is to solve the foregoing problems. In other words, an object of the present invention is to provide a toner for the development of an electrostatic image which can give solution to the problems with poor removability of spherical toner particles without causing the foregoing problem of stain of the static charger or other parts with scattered submicron particles, a process for the preparation thereof, a developer for the development of an electrostatic image and a process for the formation of an image.
The inventors made extensive studies. As a result, the inventors found the use of a toner for the development of an electrostatic image formed by externally adding to spherical toner particles a predetermined amount of agglomerated particles having a shape factor of 130 or more and a volume-average particle diameter of from 0.5 xcexcm to 10 xcexcm which are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material. It is found that such agglomerated particles, if used, are disintegrated under load developed at the forward end of the cleaning member to form irregular shape particles having a diameter of 0.2 xcexcm or less which are then effectively supplied into the edge portion of the cleaning member, making it possible to solve the foregoing problems with poor removability of spherical toner particles without causing the foregoing stain of the static charger with scattered submicron particles. In other words, the inventors found the following inventions  less than 1 greater than to  less than 19 greater than .
 less than 1 greater than A toner for the development of an electrostatic image comprising toner particles containing a binder resin and a colorant, and additive, said additive being agglomerated particles, characterized in that the agglomerated particles are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material and have a shape factor of 130or more as represented by the following equation I and a volume-average particle diameter of from 0.5 xcexcm to 10 xcexcm:
Shape factor=(ML2/A)xc3x97(xcfx80/4)xc3x97100xe2x80x83xe2x80x83(I)
wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
 less than 2 greater than The toner for the development of an electrostatic image according to Clause  less than 1 greater than , wherein the toner particles preferably have a shape factor of 125 or less and a volume-average particle diameter of 1 xcexcm or more.
 less than 3 greater than The toner for the development of an electrostatic image according to Clause  less than 1 greater than , wherein the toner particles preferably further comprise a release agent incorporated therein.
 less than 4 greater than The toner for the development of an electrostatic image according to any one of Clauses  less than 1 greater than to  less than 3 greater than , wherein the amount of the agglomerated particles is preferably from 0.3 parts by weight to 10 parts by weight based on 100 parts by weight of the sum of the amount of the toner particles and the agglomerated particles.
 less than 5 greater than A process for the preparation of a toner for the development of an electrostatic image comprising a step of preparing dispersions selected from the group consisting of the following dispersions (i) to (iii), a step of stirring or mixing the dispersions, a step of agglomerating the material thus stirred or mixture to form agglomerated particles, and a step of mixing the agglomerated particles thus formed with toner particles to obtain a toner for the development of an electrostatic image:
(i) particulate resin dispersion;
(ii) particulate lubricant dispersion; and
(iii) at least two dispersions selected from the group consisting of particulate resin dispersion, particulate lubricant dispersion and inorganic particulate material dispersion.
 less than 6 greater than The process for the preparation of a toner for the development of an electrostatic image according to Clause  less than 5 greater than , wherein the toner particles are preferably obtained by steps of mixing at least one particulate resin dispersion and at least one colorant dispersion to form mixed particles, agglomerating the mixed particles to form an agglomerate of mixed particles and heating the agglomerate to a temperature of not lower than the glass transition point of said resin so that the agglomerate undergoes coalescence.
 less than 7 greater than The process for the preparation of a toner for the development of an electrostatic image according to Clause  less than 5 greater than or  less than 6 greater than , wherein the toner particles preferably have a shape factor of 125 or less as represented by the following equation and a volume-average particle diameter of 1 xcexcm or more:
Shape factor=(ML2/A)xc3x97(xcfx80/4)xc3x97100
wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
 less than 8 greater than The process for the preparation of a toner for the development of an electrostatic image according to Clause  less than 6 greater than or  less than 7 greater than , wherein the step of forming mixed particles preferably involves the preparation of at least one release agent dispersion which is then mixed with the particulate resin dispersion and colorant dispersion.
 less than 9 greater than The process for the preparation of a toner for the development of an electrostatic image according to any one of Clauses  less than 5 greater than to  less than 8 greater than , wherein the amount of the agglomerated particles is preferably from 0.3 parts by weight to 10 parts by weight based on 100 parts by weight of the sum of the amount of the toner particles and the agglomerated particles.
 less than 10 greater than A developer for the development of an electrostatic image comprising a toner for the development of an electrostatic image and a carrier, characterized in that the toner for the development of an electrostatic image is obtained by externally adding agglomerated particles to toner particles containing a binder resin and a colorant and the agglomerated particles are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material and have a shape factor of 130 or more as represented by the foregoing equation I and a volume-average particle diameter of from 0.5 xcexcm to 10 xcexcm.
 less than 11 greater than The developer for the development of an electrostatic image according to Clause  less than 10 greater than , wherein the toner particles preferably have a shape factor of 125 or less as represented by the following equation and a volume-average particle diameter of 1 xcexcm or more:
Shape factor=(ML2/A)xc3x97(xcfx80/4)xc3x97100
wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
 less than 12 greater than The developer for the development of an electrostatic image according to Clause  less than 10 greater than or  less than 11 greater than , wherein the toner particles preferably further have a release agent incorporated therein.
 less than 13 greater than The developer for the development of an electrostatic image according to any one of Clauses  less than 10 greater than to  less than 12 greater than , wherein the amount of the agglomerated particles preferably is from 0.3 parts by weight to 10 parts by weight based on 100 parts by weight of the sum of the amount of the toner particles and the agglomerated particles.
 less than 14 greater than A process for the formation of an image comprising a step of forming an electrostatic latent image on an electrostatic carrier, a step of developing the electrostatic latent image with a developer to form a toner image on a developer carrier and a step of transferring the toner image onto a transferring material, characterized in that the developer is a toner for the development of an electrostatic image or comprises the toner for the development of an electrostatic image and a carrier, the toner for the development of an electrostatic image is obtained by externally adding agglomerated particles to toner particles containing a binder resin and a colorant and the agglomerated particles are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material and have a shape factor of 130 or more as represented by the foregoing equation I and a volume-average particle diameter of from 0.5 xcexcm to 10 xcexcm.
 less than 15 greater than The process for the formation of an image according to Clause  less than 14 greater than , wherein the toner particles preferably have a shape factor of 125 or less as represented by the foregoing equation I and a volume-average particle diameter of 1 xcexcm or more, wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
 less than 16 greater than The process for the formation of an image according to Clause  less than 14 greater than or  less than 15 greater than , wherein the toner particles preferably further have a release agent incorporated therein.
 less than 17 greater than The process for the formation of an image according to any one of Clauses  less than 14 greater than to  less than 16 greater than , wherein the amount of the agglomerated particles preferably is from 0.3 parts by weight to 10 parts by weight based on 100 parts by weight of the sum of the amount of the toner particles and the agglomerated particles.
 less than 18 greater than The process for the formation of an image according to any one of Clauses  less than 14 greater than to  less than 17 greater than , wherein the transferring step is preferably followed by a cleaning step of recovering the toner for the development of an electrostatic image remaining on the electrostatic latent image carrier.
 less than 19 greater than The process for the formation of an image according to Clause  less than 18 greater than , wherein the cleaning step is preferably followed by a recycling step of returning said toner for the development of an electrostatic image recovered at the cleaning step to the developer layer.
The present invention will be further described hereinafter.
The toner for the development of an electrostatic image of the invention is obtained by externally adding agglomerated particles to toner particles. The toner particles will be firstly described further hereinafter, followed by the description of the agglomerated particles.
The toner particles to be incorporated in the toner for the development of an electrostatic image of the invention comprises a binder resin and a colorant as main components, and optionally a release agent or release agent resin.
As the binder resin to be incorporated in the toner particles of the invention there maybe used a binder resin which has heretofore been used for toner. Thus, the binder resin to be incorporated in the toner particles is not specifically limited.
Specific examples of the binder resin employable herein include styrenes such as styrene, parachlorostyrene and xcex1-methylstyrene, acrylic monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate and 2-ethylhexyl acrylate, methylacrylic monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate, ethylenically unsaturated monomers such as acrylic acid, methacrylic acid and sodium styrenesulfonate, vinylnitriles such as acrylonitrile and methacrylonitrile, vinylethers such as vinyl methyl ether and vinyl isobutyl ether, vinylketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone, homopolymers of monomers such as olefin (e.g., ethylene, propylene, butadiene), copolymers of two or more of these monomers, mixtures of these monomers, nonvinyl condensed resins such as epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin and polyether resin, mixtures thereof with the foregoing vinyl resins, graft polymers obtained by the polymerization of vinyl monomers in the presence thereof.
As mentioned above, the toner particles of the invention may comprise a release agent or release agent resin incorporated therein. The release agent or release agent resin may be incorporated as a part of the foregoing binder resin component. Examples of the release agent employable herein include low molecular polyolefins such as polyethylene, polypropylene and polybutene, aliphatic acid amides such as silicone, oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide, vegetable-based waxes such as carnauba wax, rice wax, candelilla wax, Japan wax and jojoba oil, animal-based waxes such as beeswax, mineral and petroleum-based waxes such as montan wax, ozokerite, ceresin wax, paraffin wax, microcrystalline wax and Fischer-Tropsch wax, and modification products thereof.
At least one of these release agents is preferably incorporated in the toner particles.
As the colorant to be incorporated in the toner particles of the invention there may be used a colorant which has heretofore been known. Thus, the colorant to be incorporated is not specifically limited. Examples of the colorant employable herein include various pigments such as carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, Watchung red, permanent red, brilliant carmine 3B, brilliant carmine 6B, Du pont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, rose bengale, aniline blue, ultramarine blue, chalcoil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green and malachite green oxalate, and various dyes such as acridine-based dye, xanthene-based dye, azo-based dye, benzoquinone-based dye, azine-based dye, anthraquinone-based dye, thioindigo-based dye, dioxazine-based dye, thiazine-based dye, azomethine-based dye, indigo-based dye, thioindigo-based dye, phthalocyanine dye, aniline black-based dye, polymethine-based dye, triphenylmethane-based dye, diphenylmethane-based dye, thiazine-based dye, thiazole-based dye and xanthene-based dye. These colorants may be used singly or in combination of two or more thereof.
The toner particles of the invention may comprise various components incorporated therein besides the foregoing components to control various characteristics thereof. The particulate toner, if used as a magnetic toner, may comprise a magnetic powder (e.g., ferrite, magnetite), a metal such as reduced iron, cobalt, nickel and manganese, alloy thereof or compound containing these metals incorporated therein. If necessary, the particulate tone may further comprise various common static controllers such as quaternary ammonium salt, nigrosine compound and triphenylmethane-based pigment incorporated therein.
The toner particles of the invention comprising the foregoing components have a shape factor of 125 or less, preferably 120 or less, more preferably 118 or less, and a volume-average particle diameter of 1 xcexcm or less, preferably from 3 xcexcm to 8 xcexcm, more preferably from 4 xcexcm to 7 xcexcm. When the shape factor of the toner particles falls within the above defined range, the resulting image quality is desirable. When the volume-average particle diameter of the toner particles is too low, it is disadvantageous in that sufficient removability and developability can hardly be obtained.
The shape factor is represented by the following equation I wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
Shape factor=(ML2/A)xc3x97(90 /4)xc3x97100 (I)
The method for obtaining the toner particles satisfying the foregoing requirements is not specifically limited. Examples of the preparation method employable herein include a dry process high speed mechanical impact method which comprises applying a mechanical impact to irregular shape toner particles obtained by ordinary grinding method to make the toner particles spherical in such a manner that the foregoing requirements are satisfied, a wet melt method which comprises making irregular shape toner particles spherical in a dispersant, and method for the preparation of toner by known polymerization method such as suspension polymerization, dispersion polymerization and emulsion polymerization cohesion.
The toner particles thus obtained maybe treated with any known external additive.
The agglomerated particles to be incorporated in the toner for the development of an electrostatic image of the invention will be further described hereinafter.
The agglomerated particles to be incorporated in the toner for the development of an electrostatic image of the invention are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material.
The clause (i) will be firstly described.
The particulate resin of the invention can be made of (i) a particulate resin alone.
The material to be used as the particulate resin is not specifically limited. For example, various components described above as binder resin may be used.
These resin components may be subjected to existing known resin grinding method or existing emulsification or dispersion method in a liquid medium such as water and organic solvent to prepare a desired particulate resin. For example, a polymerization method in a nonuniform dispersion system such as emulsion polymerization, suspension polymerization and dispersion polymerization may be effected to easily obtain a particulate resin dispersion having the particulate resin dispersed therein. Any other methods such as method which comprises adding a uniformly polymerized particulate resin obtained by solution polymerization or bulk polymerization to a solvent in which the polymer cannot be dissolved together with a stabilizer may be effected to obtain a particulate resin dispersion having the particulate resin dispersed therein.
In the case where a vinyl-based monomer is used to obtain the particulate resin, emulsion polymerization method or seed polymerization method using an ionic surfactant, preferably in combination with a nonionic surfactant, may be effected to prepare a particulate resin dispersion. Other resins, if it is oil-based and can be dissolved in a solvent having a relatively low water solubility, may be dispersed in water in the form of solution in the solvent together with an ionic surfactant or high molecular electrolyte by means of a dispersing machine such as homogenizer to prepare a fine aqueous dispersion which is then heated or put under reduced pressure to vaporize the solvent, thereby preparing the desired resin dispersion.
Examples of the surfactant employable herein include anionic surfactants such as sulfuric acid ester salt-based surfactant, sulfonic acid salt-based surfactant, phosphoric acid ester-based surfactant and soap-based surfactant, cationic surfactants such as amine salt-based surfactant and quaternary ammonium salt-based surfactant, nonionic surfactants such as polyethylene glycol-based surfactant, alkylphenol ethylene oxide adduct-based surfactant and polyvalent alcohol-based surfactant, and various graft polymers. Thus, the surfactant to be used herein is not specifically limited.
Alternatively, the particulate resin of the invention can be made of (ii) a particulate lubricant alone.
The lubricant to be used in the invention is adapted to accelerate slippage of the cleaning member with a carrier such as photoreceptor and hence reduce friction therebetween.
Examples of the lubricant employable herein include graphite, molybdenum disulfite, zinc stearate, calcium stearate, and magnesium stearate. Further examples of the lubricant employable herein include those described above as release agent, e.g., low molecular polyolefins such as polyethylene, polypropylene and polybutene, aliphatic acid amides such as silicone, oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide, vegetable-based waxes such as carnauba wax, rice wax, candelilla wax, Japan wax and jojoba oil, animal-based waxes such as beeswax, mineral and petroleum-based waxes such as montan wax, ozokerite, ceresin wax, paraffin wax, microcrystalline wax and Fischer-Tropsch wax, and modification products thereof.
These lubricant components may be subjected to existing mechanical grinding method or emulsification or dispersion method in a liquid medium in the same manner as with the foregoing particulate resin to prepare a particulate lubricant or particulate resin dispersion.
Further, the agglomerated particles of the invention are made of (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material. In other words, he agglomerated particles of the invention are made of (iii)-(a) a particulate resin and a particulate lubricant, (iii)-(b) a particulate resin and an inorganic particulate material, (iii)-(c) a particulate lubricant and an inorganic particulate material or (iii)-(d) a particulate resin, a particulate lubricant and an inorganic particulate material.
As the material of the particulate resin and particulate lubricant there may be used those described above.
Examples of the material of the inorganic particulate material employable herein include silica, alumina, zinc oxide, cerium oxide, iron oxide, strontium titanate, titanium oxide, calcium carbonate, magnesium carbonate, and tricalcium phosphate.
The shape of the inorganic particulate material is preferably irregular shape such as acicular having a great aspect ratio as represented by the ratio of long axis length to short axis length.
These inorganic particulate materials may be subjected to existing mechanical grinding method or emulsification or dispersion method in a liquid medium in the same manner as with the foregoing particulate resin to prepare an inorganic particulate material or inorganic particulate material dispersion.
The foregoing particulate resin, particulate lubricant or inorganic particulate material may be prepared in the manner as mentioned above. The particle diameter of these particulate materials is preferably 0.2 xcexcm or less.
The process for the preparation of agglomerated particles made of two or more of the foregoing particulate materials is not specifically limited. In practice, however, the agglomerated particles can be prepared in the following manner. Examples of the preparation method employable herein include a method which comprises mechanically mixing the foregoing particles in dry process to form agglomerated particles, an electrical agglomeration method in a liquid medium, and a physical agglomeration using a high molecular flocculating agent.
In this case, the system can be optionally heated during or after the preparation of agglomerate to control the cohesive force or adhesivity between the particulate resin and/or particulate lubricant and the inorganic particulate material, making it possible to adjust the strength of the agglomerated particles against disintegrating force.
The method for the preparation of agglomerated particles made of two or more of the foregoing particulate materials will be briefly described in connection with specific examples. In some detail, various dispersions having these particulate materials dispersed therein are mixed to form mixed particles which are then agglomerated to form an agglomerate of mixed particles, thereby preparing agglomerated particles. In the case where the agglomerated particles contain a particulate resin or particulate lubricant, the foregoing agglomerate is preferably heated to a temperature of not lower than the glass transition point of the particulate resin or particulate lubricant to undergo coalescence, thereby forming agglomerated particles.
The agglomerate thus prepared acts as a sealing compound in the edge portion of the cleaning member in the image forming apparatus. Thus, the volume-average particle diameter of the agglomerate is from 0.5 xcexcm to 10 xcexcm, preferably from 0.7 xcexcm to 5 xcexcm, more preferably from 1 m to 3 xcexcm. When the volume-average particle diameter of the agglomerate falls below 0.5 xcexcm, the particles can be easily scattered inside the developing machine, giving a tendency toward stain in the interior of the image forming apparatus. On the contrary, when the volume-average particle diameter of the agglomerate exceeds 10 xcexcm, the agglomerated particles cannot be sufficiently supplied as sealing compound into the edge portion of the cleaning member, occasionally making it impossible to obtain good removability.
The agglomerated particles of the invention preferably have a shape factor of 130 or more, more preferably from 135 to 150, even more preferably from 140 to 145. When the shape factor of the agglomerated particles is too low, a tendency is given that the agglomerate cannot sufficiently act as a sealing compound. The shape factor is represented by the following equation I where ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
Shape factor=(ML2/A)xc3x97(xcfx80/4)xc3x97100(I)
The agglomerated particles of the invention are preferably free of colorant. This is because even when some of the agglomerated particles of the invention are transferred and fixed on the final image together with the toner particles, image defects must be prevented.
By externally adding the agglomerated particles thus obtained to the foregoing toner particles at a predetermined mixing ratio, the toner for the development of an electrostatic image of the invention, particularly accomplishing high image quality and good removability at the same time, can be prepared.
In this case, the proportion of the agglomerated particles is from 0.3 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, more preferably from 1 to 3 parts by weight based on 100 parts by weight of the sum of that of the toner particles and the agglomerated particles.
When the added amount of the agglomerated particles falls below 0.3 parts by weight, a tendency can be given that a sufficient cleaning effect cannot be exerted. On the contrary, when the added amount of the agglomerated particles exceeds 10 parts by weight, a tendency can be given that the resulting toner has remarkably impaired chargeability and fluidity.
The toner for the development of an electrostatic image thus obtained can be used as a one-component developer comprising the toner alone or a two-component developer comprising the toner and a carrier.
The toner for the development of an electrostatic image thus obtained can be used in the following image forming method. In other words, the toner for the development of an electrostatic image of the invention is preferably used in an image forming method comprising a step of forming an electrostatic latent image on an electrostatic carrier, a step of developing an electrostatic latent image with a developer to form a toner image on a developer carrier and a step of transferring the toner image onto a transferring material, wherein the developer is the foregoing toner for the development of an electrostatic image or comprises the toner for the development of an electrostatic image or a carrier.
In the image forming method, the transferring step is preferably followed by a cleaning step of recovering the toner for the development of an electrostatic image remaining on the electrostatic latent image carrier.
Further, in the image forming method, the cleaning step is preferably followed by a recycling step of returning the toner for the development of an electrostatic image recovered at the cleaning step to the developer layer.